Khan, 29, came to his senses well after the bout had been decided and was taken to the hospital. He later tweeted out a photo assuring he was fine.
"Im okay everyone, that's boxing for you, congrats to @Canelo monster punch, much love to all the fans!" tweeted Khan, who moved up two weight divisions to take on Alvarez.
Alvarez said he proved he was much more than just raw power.
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"Like I said from the beginning, I knew he was very fast and knew it would be competitive in the beginning," he told reporters. "But I knew time would come to my favor, and you saw that.
"Many people focus on my power and talk to my power but I have many more qualities in the ring. I like to surprise everyone."
The former WBA and WBC super welterweight champion, who lost both world titles on a majority decision to Floyd Mayweather Jr. in 2013, entered the night as a heavy favorite but Khan (31-4, 19 knockouts) seemed to control the first couple of rounds with his hand speed.
The Mexican power-puncher caught up with Khan in the third round and began to cut off the ring and push his opponent against the ropes. In the fifth, Khan absorbed a left hook and sustained a cut over his right eye.
It all led to the crushing closer where 25-year-old Alvarez again showed the brute strength that has now carried him to a record of 47-1-1 with 33 knockouts.
Following the fight, Alvarez invited WBA-IBF champion Gennady "Triple G" Golovkin into the ring, fuelling the growing clamour for a clash between the two.
"I'll fight him right now. Let's put the gloves on and get in there with him," Alvarez said.
"I fear no one in this sport."
(Writing by Jahmal Corner in Los Angeles; editing by Amlan Chakraborty)
